Looking for advice/help on doing a Catalytic Oxalic Acid soak for P0420 and P3190 in SoCal

I'm thinking about trying the oxalic/citric acid soak method to get some more miles out of my 2005 Gen 2 Prius. I have been getting the P0420 and P3190 codes for (too many) months (where I haven't been driving it as much as I normally would, and using transit and rentals when needed). The car has burned oil for a while and has 190K miles. It has an OEM HV battery and major cosmetic issues so functionally may still be worth more to keep it running than to sell/scrap, but $3K for a new cat in CA is tough (and getting a new car is also tough).

I also had a P0505 code for a few weeks as well, had the car not turning off the ICE at stops, increasing exhaust fumes and rough idling. Eventually I had some misfires one day when I turned it on. With the misfires I turned it off immediately and did a throttle body cleaning myself, which I found was filthy with oil/residue. That stopped the misfires and the codes haven't come back yet, but the cat is still loud, and the idea is rough at times (the roughness comes and goes). My mechanic says the soak won't work, that I just need a new cat, but I haven't looked at the cat itself, and I'm inclined to think the soak method is outside of normal mechanics' experience and am interested in trying this if it might work.

Anybody get this to work for an ongoing/longer basis? Did it work on cars where the cat was making noise, and did the soak clear that noise/power issue, and not just clear the code? Anybody locally in SoCal that's done this that's willing to help me walk thru it (and maybe have a place to do it and/or maybe a mechanic familiar with this - I live in an apt, but will figure something out)? I have to stop by the mechanic to get the cat shield removed, and then maybe figure out the soak... I haven't done much work on cars myself but at least was able to figure out cleaning the throttle body due to Youtube.

Thanks

 

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